Pneumatic tire

Abstract

In a pneumatic tire wherein the aspect ratio is at most 0.6, the carcass reinforcement, seen in meridian section, follows its natural equilibrium profile between the zone of contact of the side walls with the tread reinforcement and the zone of contact of the side walls with the respective bead rings. The profile is tangent to the bead rings, and the bead rings themselves have a reinforced torsional rigidity.

I claim: 
     
       1. A pneumatic tire comprising a tread, a pair of side walls respectively extending inwardly from the edges of the tread, a pair of beads respectively at the inner edges of the side walls, a pair of bead rings respectively reinforcing said beads, a carcass reinforcement formed of radial cords anchored to the bead rings, a tread reinforcement formed with reinforced edges and comprising at least two plies of cords parallel in each ply and crossed from one ply to the other at a slight angle with respect to the circumferential direction of the tire, the aspect ratio H/B of the height H on the rim to the largest axial width B of the carcass reinforcement being at most equal to 0.6, characterized in that, when the tire is mounted on a rim and inflated, the rim being of standard diameter and the rim width being substantially equal to the width of the tread reinforcement, then the carcass reinforcement, seen in meridian section, follows its natural equilibrium profile between the zone of contact of the side walls with the tread reinforcement and the zone of contact of the side walls with the respective bead rings, said profile meeting the bead rings in tangent relation and the bead rings themselves comprising three members, each of said members being tangent to two others of said members, the bead rings thus having a reinforced torsional rigidity. 
     
     
       2. A pneumatic tire according to claim 1, characterized in that the tread reinforcement has a meridian curvature at most equal to its curvature in the longitudinal direction. 
     
     
       3. A pneumatic tire according to claim 1, characterized in that, between the zone of contact of the carcass reinforcement with the tread reinforcement on the one hand and the zone of contact of the carcass reinforcement with the bead rings on the other hand, the equilibrium profile of the carcass is defined by the equation   cos φ = (R.sup.2 = R.sub.e.sup.2)/(R.sub.s.sup.2 = R.sub.e.sup.2)     where φ is the angle formed by (1) the tangent to the equilibrium profile and (2) the axis of rotation of the tire, the tangent being at a radius R from said axis; R e  is the radius of the equilibrium profile corresponding to the maximum axial width reached in the side walls by this profile; and R s  is the radius of the point of the tread farthest from the axis of rotation.   
     
     
       4. A pneumatic tire according to claim 1, characterized in that the common tangent to the carcass reinforcement and at least one bead ring forms, with the axis of the tire, an angle φ t  which satisfies the condition   cos φ.sub.t = (R.sub.t.sup.2 - R.sub.e.sup.2)/(R.sub.s.sup.2 - R.sub.e.sup.2)     where R t  is the radius of the zone of contact of the carcass with the bead ring; R e  is the radius of the equilibrium profile corresponding to the maximum axial width reached in the side walls by this profile; and R s  is the radius of the point of the tread farthest from the axis of rotation.   
     
     
       5. A pneumatic tire according to claim 1, characterized in that the length Σ of the carcass between the zone of contact thereof with the tread reinforcement, of radius R a , and the zone of contact of the latter with the least one bead ring, of radius R t , satisfies the equation ##EQU2## where R e  is the radius of the equilibrium profile corresponding to the maximum axial width reached in the side walls by this profile; R s  is the radius of the point of the tread farthest from the axis of rotation; and R is the radius of the equilibrium profile at any point between R t  and R a .